FlyBase is a database of the core genetic and genomic information on the major genetic model organism, the fruit fly, Drosophila melanogaster, and related organisms of the family Drosophilidae. D. melanogaster has been, and continues to be the pioneering organism in understanding the intricate interplay of genes and their encoded products to drive complex biological processes such as the formation of the body plan of an embryo or the wiring of the nervous system. The evidence that such complex biological events has an ancient origin, predating the split of the insect and vertebrate lineages, means that the fundamental studies on complex biological processes that are carried out in D. melanogaster directly impact on our understanding of comparable processes in human biology and disease. Indeed, the majority of human genes associated with disease have closely related genes in Drosophila. The very vibrant Drosophila research community continues to carry out a great deal of fundamental research, and it is imperative to the progress of the scientific community as a whole that there is a central resource that captures, organizes and presents this information in a way that is readily accessible not only to experts in the fly, but to the broader research community. FlyBase serves that role, and captures the primary information on the DNA sequence of the D. melanogaster genome and related genomes, as well as its encoded transcripts and proteins, classical and transgenic mutations, phenotypes, strain collections, etc. These data can be accessed as a public resource, without restriction, by means of the Internet or as bulk downloads, and are organized so that complex queries of the Drosophila literature and genome projects can be carried out. Specific goals for the next 5 years of the FlyBase project, based on information garnered from the scientific literature and from large-scale data producers, will include capture, organization and presentation of: (1) a comprehensive set of annotations attached to the Drosophila genomic sequence, both in terms of the encoded products as well as the sites on the DNA that mediate regulation of gene expression and the architecture of chromosomes, (2) information on the basic genetics of genes and their mutant alleles, and (3) the relationship of the fundamental genetic/genomic objects described in items 1 and 2 to each other, e.g., their location on chromosomal and sequence maps, their interactions to produce the regulatory circuitry of cells, tissues and whole organisms, their anatomical distribution, both spatially and temporally, and their variation in populations and phenotypic classes.